The present invention deals with disc drives. A typical disc drive includes one or more magnetic discs, which are mounted on a hub or spindle. When a plurality of discs are to be mounted on a hub, the discs are separated along the axial direction of the hub by spacers mounted between the discs. The disc, or plurality of discs, are mounted on a flange portion of the hub by a clamp apparatus. The clamping is such that the disc(s) rotate with the hub about the radial center axis of the hub. The primary method of disc clamps in prior art results in a vertical force point contact about a circumference point on the disc. This point contact can add additional warping to the disc itself.
A typical disc assembly will also include a transducer(s) that is supported by an air bearing which flies above the surface of each disc. The transducer and air bearing are typically referred to as the read/write (R/W) head. A drive controller controls the disc drive movement to allow retrieval of information from the magnetic disc (or writing of data to the disc). An electromechanical actuator operates to move the data head radially over the disc surface for track seek operations and holds the transducer directly over a track for R/W operations.
Modern high performance disc drives employ head positional servo loops. The function of the head positioning servo system within the drive is to position the read/write head over a data track with sufficient accuracy to enable reading and writing of that track without error and to position the write element with sufficient accuracy not to encroach upon adjacent tracks to prevent data erosion from those tracks during writing operations to the track being followed. In order to satisfy these requirements, the tracking system must be designed to reject disturbances. These disturbances include noise from sources such as spindle bearings, air turbulence, etc., and can be classified into two general categories, those that generate repeatable runout (RRO) and those that generate non-repeatable runout (NRRO). The term “repeatable” is used to describe periodicity on a revolution-by-revolution basis as opposed to a track-by-track basis. The response of the head positioning servo system to the RRO and NRRO sources is track miss-registration (TMR).
Embedded servo systems derive head position information from servo information interspersed within the data blocks written on a surface of a rotating magnetic disc. One advantage of employing embedded servo information is that the same head and electronics are used to read both user data and head position information. One of the major sources of RRO is the servo write process that occurs during disc drive manufacturing. The NRRO disturbance (bearing noise, air turbulence, servo writer vibration, etc.,) that occurs during servo write is essentially frozen into the written position information and becomes the RRO for the particular track.
It is known with a disc drive how to extract and correct for RRO. Embedded servo fields are recorded on disc surfaces and are used by a servo controller in accurately aligning a read/write head over a desired track.
Disc assemblies typically have air filtration systems to expunge any air borne particles at start up. Air passing through a filter will carry any minute matter into the filter to avoid disc contamination by such particles.
U.S. Pat. No. 4,885,652 dated Dec. 5, 1989 to Leonard et. al titled ‘Disk Cartridge’ provides an air filter and ribs incorporated into the inner surface of the cartridge, which induce the air in the cartridge to flow toward the air filters. When the disc is rotated at high speed within the cartridge, airflow induced by disc rotation is directed toward the air filters by the ribs adjacent to the outer circumference of the disc it also is employed between the disc and filter and induces internal airflow generated by rotation of the disc toward the air filter(s). The present invention will address ways of improving air flow in a hard disc device.
Clamping of the disc on the hub is done prior to derivation of the embedded servo information. Improper clamping can add to creation of additional disc warping along an annular track. Additional warping can cause the air bearing to have an inconsistent flying height above the surface of each disc effecting the head pick-up amplification. This is commonly referred to as axial run out. Point contact clamping apparatus can also affect non-operational shock tolerance of the disc assembly. Clamping that causes additional warping of the disc will also effect RRO and track squeeze. As disc drives become smaller, there is a tendency for the discs to warp into a potato chip type shape due to the required clamping force of the disc clamp to prevent any ‘disc slippage’. Typical warping may be somewhat sinusoidal extending outward from the point of each fastener contact. Thus, a combination of annular point contact and fastener contact will distort the flatness of a disc in a non-uniform manner. All manufactured disc drives have drop specifications, which are a force expressed in g's. All of these factors necessitate an improvement in disc clamping.
The present invention addresses these and other problems, and offers other advantages over the prior art by improvements in a disc clamp apparatus.